1. Field of the Invention
Invention relates to masks, also known as photomasks, used in photolithography processes and, more particularly, to a method for applying level-set technology to time-evolve contours representing patterns on photomasks in such a way so as to allow for production of wafer patterns with minimal distortions or artifacts and to allow for the ability to constrain resulting contours to rectilinear patterns.
2. Description of the Related Art
Lithography processing represents an essential technology for manufacturing Integrated Circuits (IC) and Micro Electro-Mechanical Systems (MEMS). Lithographic techniques are used to define patterns, geometries, features, shapes, et al (“patterns”) onto an integrated circuit die or semiconductor wafer or chips where the patterns are typically defined by a set of contours, lines, boundaries, edges, curves, et al (“contours”), which generally surround, enclose, and/or define the boundary of the various regions which constitute a pattern.
Demand for increased density of features on dies and wafers has resulted in the design of circuits with decreasing minimum dimensions. However, due to the wave nature of light, as dimensions approach sizes comparable to the wavelength of the light used in the photolithography process, the resulting wafer patterns deviate from the corresponding photomask patterns and are accompanied by unwanted distortions and artifacts.
Techniques such as Optical Proximity Correction (OPC) attempt to solve this problem by appropriate pre-distortion of the photomask pattern. However, such approaches do not consider the full spectrum of possible photomask patterns, and therefore result in sub-optimal designs. The resulting patterns may not print correctly at all, or may not print robustly. Accordingly, there is a need for a method for generating the optimal photomask patterns which result in the robust production of wafer patterns faithful to their target patterns.